1. Field of the Invention
The invention relates generally to electrical switching apparatus and, more particularly, to yoke assemblies for electrical switching apparatus, such as circuit breakers. The invention also relates to spring assemblies for circuit breaker yoke assemblies.
2. Background Information
Electrical switching apparatus, such as circuit breakers, provide protection for electrical systems from electrical fault conditions such as, for example, current overloads, short circuits, abnormal voltage and other fault conditions. Typically, circuit breakers include an operating mechanism which opens electrical contact assemblies to interrupt the flow of current through the conductors of an electrical system in response to such fault conditions as detected, for example, by a trip unit.
Among other components, the operating mechanisms of some low-voltage circuit breakers, for example, typically include a pole shaft and a spring assembly. The pole shaft is pivotable among an open position, corresponding to the electrical contact assemblies being open (e.g., contacts separated), and a closed position, corresponding to the electrical contact assemblies being closed (e.g., contacts electrically connected). The spring assembly includes at least one spring that is typically coupled to the circuit breaker housing and, directly or indirectly, to the pole shaft. The spring or springs is/are structured to bias the pole shaft, for example, to facilitate opening of the electrical contact assemblies.
It is desirable to optimize the operation of the spring assembly, in order to improve circuit breaker performance, for example, by enabling the electrical contact assemblies to open rapidly. It is also desirable to minimize the space required for the spring assembly. These two objectives are somewhat contradictory, and are difficult to achieve because of the limited amount of space that is available within the circuit breaker. This is particularly true in view of the increasing trend to minimize the overall size of the circuit breaker. It is, therefore, difficult to effectively arrange the spring assembly and/or related structures within the circuit breaker housing in a manner that affords the desired leverage and spring energy. In this regard, known circuit breaker designs leave much to be desired.
There is, therefore, room for improvement in electrical switching apparatus, such as circuit breakers, and in spring assemblies therefor.